1. Field of the Invention
This invention relates to a solenoid valve manifold and assembly wherein a solenoid pilot change-over valve including a main or change-over valve having a valve body and a solenoid pilot valve provided on the valve body for controlling the change-over valve is placed on a manifold body.
2. Description of the Prior Art
Conventionally, solenoid pilot change-over valves are divided into two types including an internal pilot type wherein a pressure medium for the pilot operation is supplied from the inside of a change-over valve serving as a main valve into a solenoid pilot valve, and an external pilot type wherein a pressure medium for the pilot operation is supplied separately from the outside of a change-over valve into a solenoid pilot valve. Solenoid pilot change-over valves of the two types are conventionally produced separately from each other.
A solenoid pilot change-over valve of the internal pilot type is disclosed, for example, in Japanese Patent Publication No. 12990/1989. General construction of the conventional solenoid pilot change-over valve is shown in FIG. 12. Referring to FIG. 12, a spool 4 having four pistons 3 thereon is fitted for sliding movement in an axial direction thereof in a valve body 2 of a change-over valve 1 serving as a main valve such that a pair of pilot chambers 5 may be formed adjacent the opposite axial ends of the spool 4. A pair of solenoid pilot valves 6 are provided on the opposite axial outer ends of the valve body 2. In FIG. 12, the change-over valve 1 and solenoid pilot valves 6 are shown integrated with each other for the convenience of illustration.
An inlet port 7 and two outlet ports 8 as well as two exhaust ports 9 are formed in the valve body 1. A plunger 11 is fitted for sliding movement in an axial direction in a plunger chamber 10 of each of the solenoid pilot valves 6, and a solenoid 12 is disposed around each of the plunger chambers 10. Each of the plunger chambers 10 is connected to a corresponding one of the pilot chambers 5 by way of a connecting path 13. A pilot valve seat 15 and an atmosphere communicating valve seat 16 are provided in an opposing relationship to each other in each of the pilot chambers 5. The pilot valve seats 15 are connected to the inlet port 7 by way of a pilot path 14 while the atmosphere communicating valve seats 16 are opened to the atmosphere. Each of the plungers 11 is normally urged toward the corresponding atmosphere communicating valve seat 16 by a sprint 17 so that it normally closes the atmosphere communicating valve seat 16 but opens the pilot valve seat 15 of the corresponding solenoid pilot valve 6. It is to be noted that the pilot path 14 is connected to neither of the two outlet ports 8 and the two exhaust ports 9.
When the solenoid 12 of the left-hand side one in FIG. 12 of the solenoid pilot valves 6 is energized without energizing the solenoid 12 of the other right-hand side solenoid pilot valve 6, the plunger 11 of the left-hand side solenoid pilot valve 6 opens the atmosphere communicating valve seat 16 and closes the pilot valve seat 15 while the plunger 11 of the right-hand side pilot valve 6 opens the pilot valve seat 15 and closes the atmosphere communicating valve seat 16. Accordingly, the right-hand side pilot chamber 5 is communicated with the inlet port 7 by way of the thus open pilot valve seat 15 of the right-hand side solenoid pilot valve 6 and the pilot path 14 so that a pressure medium (compressed air in this instance) is supplied from the inlet port 7 into the right-hand side pilot chamber 5 while the left-hand side pilot chamber 5 is disconnected from the inlet port 7 by the left-hand side plunger 11. Consequently, the spool 4 is displaced leftwardly as seen in FIG. 12. On the contrary if the solenoid 12 of the right-hand side solenoid pilot valve 6 is energized while the solenoid 12 of the left-hand side solenoid pilot valve 6 is not energized, the left-hand side pilot chamber 5 is communicated with the inlet port 7 while the right-hand side pilot chamber 5 is disconnected from the inlet port 7. Consequently, the spool 4 is displaced rightwardly.
FIG. 13 shows an exemplary one of conventional solenoid pilot change-over valves of the external pilot type. Referring to FIG. 13, the solenoid pilot change-over valve shown has generally similar construction to that of the solenoid pilot change-over valve of the internal pilot type of FIG. 12 described just above but is different in that an external pilot port 18 is formed in the valve body 2 and connected to the pilot valve seats 15 of the two solenoid pilot valves 6 by way of the pilot path 14 and a pressure medium for the pilot operation is introduced into the solenoid pilot change-over valve by way of the external pilot port 18 separately from a pressure medium which is alternatively introduced into the solenoid pilot change-over valve by way of the inlet port 7.
In this manner, the conventional solenoid pilot change-over valve of the internal pilot type and the conventional solenoid pilot change-over valve of the external pilot type are different from each other in structure of the change-over valve serving as a main valve, and accordingly, they are conventionally produced separately as solenoid pilot change-over valves for the individual exclusive use, which, however, is uneconomical. Also in use, particularly where a comparatively large number of solenoid pilot change-over valves are installed on a manifold and used at a time, in the case of the solenoid pilot change-over valve of the external pilot type, a pipe for the supply of external pilot pressure must be connected to each of the solenoid pilot change-over valves. Consequently, the cost for such pipes is high, and besides, such pipes are complicated in arrangement.